pkgbase: add a mechanism to be able to force a give ucl include

This is made in order to be able to find add the post-install scripts
for the kernel, where PKGNAME varies for each KERNCONF but we don't want
to dynamically duplicated the kernel.ucl file.

At the same time we don't want the *-dbg* packages to actually include
those post-install scripts

pkgbase: rework certctl package to only run rehash on the main package

Rework how ucl manifest are generated leveraging ucl features and flua

now the ucl generation is done via a lua script which uses libucl to
ingest the template and use variables as defined in its command line.

the template will include only if it exist a ucl file named after the
package name which will complement the template or overwrite what was
defined in the template if defined in this specific ucl file

this allows to overwrite license, but add script only to the packages
who actually needs them.

As a results the post install scripts are now only added to the right
package and not also added to the subpackages like -man or -dev

Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D44374

Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

pkgbase: make only vital packages vital, not their sub-packages

make "vital" a replaceable, which defaults to "false" and only set it for
the main clib, utilities and runtime packages, not their sub-packages

PR: 254174
Differential Revision: https://reviews.freebsd.org/D29224

pkgbase: Add PKG_NAME_PREFIX, PKG_MAINTAINER and PKG_WWW

This is useful for downstream users to customize the packages.
Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D26019

Add FreeBSD RCSID header and svn:keyword property.

Sponsored by: The FreeBSD Foundation

Rework the way <packagename>.ucl files are generated.
One of the major pain points with how this was implemented
is the requirement of in-tree, hard-coded <name>.ucl, as
well as <name>-<suffix>.ucl where <suffix> can be lib32,
profile, development, debug, or any combination of the four.

This created significant overhead when adding new packages
and any of the files in any of the combinations were missing.

Instead of test(1)-ing if the <packagename>.ucl file exists,
hand off to a script to figure out what the final ucl file
name should be before invoking pkg(8).

The default behavior is 'template.ucl' is used as a fallback.

This affects only the userland packages, as the kernel code
is already smart enough to handle these variations.

Sponsored by: The FreeBSD Foundation